This invention relates to a back support control mechanism for a chair or the like. The invention is directed to providing adjustable positioning of a back support with respect to a seat in an infinite number of positions in a range of movement of the back support.
In the past, back support control mechanisms have been employed, permitting a back support of a chair to be moved forwardly and rearwardly with respect to a seat through a range of movement, but limited to discrete positions within the range rather than an infinite number of positions within that range. Other arrangements have been employed, using a threaded shaft, which does provide for infinite adjustment within the range, but which is relatively cumbersome to use since it requires the turning of a control knob a large number of times to complete movement of the back support throughout its entire range of travel. Adjustment of the back support in such mechanisms is relatively slow and time consuming. Other arrangements have been utilized, incorporating a slotted support and lock nuts which must be loosened and tightened every time the back support is moved.
The present invention provides an infinitely adjustable back support control mechanism which overcomes the disdvantages noted above. Adjustment of the back support is achieved easily and quickly over any portion or all of the range movement of the back support. The invention involves use of a pressure pad fixed with respect to the back support which is positioned within a channel member that is fixed with respect to the seat. The pressure pad may slide within the channel member, limited in its movement therein by a stop pin. A lever is coupled to the pressure pad and is movable therewith and with respect thereto, and a cam surface on the lever exerts pressure against the pressure pad through a spring plate. Close manufacturing tolerances which would otherwise be required are obviated by use of the spring plate. The lever in one position permits free movement of the pressure plate within the channel member. In another position of the lever, the pressure plate is made to bear against the channel member to prevent further movement of the pressure pad, thereby fixing the position of the back support with respect to the seat.
The back support is preferably a tubing that includes a carrier therein that holds the pressure pad. That carrier preferably is formed of side rails, with the pressure pad being supported between the rails. The rails in turn ride on tracks along the sides of the channel member. The channel member is positioned within the tubing that forms the back support, and hence the entire adjustment mechanism is basically concealed from view, with the exception of the operating lever which extends beneath the back support tubing in a position convenient for access thereto. The lever is simply actuated to permit adjustment of the back support, and then returned to a back support locking position in which the pressure pad is firmly in engagement with the channel member.
Thus a compact back support control mechanism is provided, simple to use and generally obscured from view, permitting infinite adjustment of the back support with respect to the seat.
The invention will be more completely understood by reference to the following detailed description of a presently preferred embodiment thereof .